What about adding a dialogue to the tower lord that allows the player to trigger a personal event for scouting the tower which will last for 15-20 minutes where he has to be inside or nearby the tower?
The reward will be in silver and WXP and you will be able to trigger the event once per account (or per character) per tower. This will prevent the event from being farmed and would (hopefully) also motivate more players to scout the towers and add some sort of rotation between scouts and towers.
Maybe adding some upgrade options to the tower to enhanche the reward based on the tier and/or some sort of personal “bonus” if, while the event is active, there will be a succesful defense.
I apologize if i misspelled something or if my post isn’t clear, english is not my first language